The present invention relates to a structure and method for use in tests of circuit chips, and more particularly relates to a method and structure for making temporary connections between circuit chips and a temporary chip carrier for use in conducting burn-in tests of the circuit chips.
As semiconductor devices become smaller and their density increases there is a corresponding increase in overall chip failure rates. Semiconductor manufacturers are challenged to ensure that chips are tested and known to be good, “known good die” (KGD), before being used in the next level of assembly, which typically is attachment to a substrate or board. There is therefore a need to identify and eliminate defective chips before they are attached to a product. Burn-in processes have been developed to identify and eliminate the use of defective chips. This burn-in test electrically operates the chip at elevated voltage and temperature levels for an extended period of time to simulate the actual operation of the chip for its normal and expected lifetime in a final product by monitoring the electrical responses of the chip and thereby screen out defective chips. The testing may also involve a “speed sort”, separating and categorizing chips that operate at various levels of performance to be used in various products.
A Temporary Chip Attach (TCA) carrier, typically a substrate or board, is provided for testing the chips. The TCA carrier has electrical contacts which correspond to the electrical contacts on the semiconductor chip. The chip is typically positioned on the chip carrier so that the solder connections on the chip are aligned with the corresponding electrical contacts on the chip carrier. The solder connections are then reflowed to make electrical connections between the chip and chip carrier. After burn-in the chip is removed from the TCA carrier. This is typically accomplished by a shear or tensile process, either at room or elevated temperatures.
The known good chip is then reconditioned for use in functional product. The reconditioning is typically a thermal process to restore the geometry of the solder connection on the chip. Since good chips will be subsequently attached to product it is necessary to remove the chip from the TCA carrier after burn-in with a minimum amount of force to avoid damage to the chip. The same TCA carrier may then be used for testing additional chips. It is therefore desirable to temporarily attach the semiconductor chip to the chip carrier in such a way that both can be easily separated after burn-in without mechanical damage to either the semiconductor chip or the TCA carrier.
Various methods are known for building such TCA carriers, most of which involve some form of thin film technology. The prior art process of producing temporary chip carriers typically involve the use of photolithographic techniques and/or masks in order to reduce the area actually in contact between the TCA carrier and the solder connections on the semiconductor device. The thin film structures are usually metallic or polymeric. The intent of the thin film structure is to reduce the force necessary for chip removal by reducing the overall joining area between the chip carrier and chip electrical connection.
There is therefore a need to avoid using thin film processing, typically an expensive and a time consuming operation. Thus, a purpose of the present invention is to have a method for providing a temporary chip attach carrier which does not require thin films.
These and other purposes of the present invention will become more apparent after referring to the following description considered in conjunction with the accompanying drawings.